Certain fire safety systems capable of controlling fluids are based on sensitive means installed punctually at a location liable to be exposed to the heat of the fire. There are, for example, sprinkler nozzles intended to be mounted on conduits for supplying fluid for extinguishing the fire. The fluid is pressurized in the pipeline and acts against a valve held firm by an ampoule filled with alcohol. During the fire, the bulb explodes under the effect of the pressure exerted by the alcohol which vaporizes and releases the flap, which allows the fluid to exit and to water the fire in order to extinguish it.
Also known are valves installed in ventilation ducts and kept open against a closing spring. A sensitive element is held in the duct in order to release the spring and to close the valve in case of untimely elevation of the temperature in the conduit. The sensitive element is, for example, a form of two elements broken apart by a low melting eutectic alloy, for example, at 70° C. The two elements separate when the alloy melts and releases the valve. This may also be a shape memory spring.
Safety valves are also located on reservoirs of fluid under pressure, in order to release the fluid in the event of a fire and thus limit the risks of explosion. Such valves are used, for example, for vehicles operating with combustible gas to evacuate the gas in a well-defined zone in the event of a fire.
These solutions have the advantage of being passive, that is to say they do not use external energy to obtain control. However, they have the disadvantage of being sensitive only at a point location. In particular, in the case of a large tank, a part of the reservoir could be exposed to heat, while the sensitive element could be exposed only to moderate heat, thus insufficient to control the opening of the safety valve.
The object of the invention is to provide a passive control safety valve whose sensitive element is not limited to a point sensitivity.